The general purpose of this project is to explore the molecular basis of active transport in microorganisms. Thanks to the work of several laboratories there is now good evidence that in many cases the linkage between metabolism and transport systems is effected by a circulation of protons across the cytoplasm membrane, a concept first proposed by Peter Mitchell as part of the chemiosmotic theory. Metabolic pathways bring about the extrusion of protons and thus generate a gradient of pH and of electrical potential; this proton motive force is the immediate energy donor for many transport systems (and also for oxidative phosphorylation, motility and other work functions). However, we also recognize a growing number of transport systems that utilize ATP or a related substance, by a mechanism that remains unknown. The nature of this ATP requirement will be the focus of next year's work. We are concentrating on Streptococcus faecalis, an organism that offers both technical and conceptual advantages. The main lines of investigation are the transport system for K ion, an electrogenic primary pump that requires both ATP and the membrane potential; and ATP-induced movement of ions and other metabolites into and out of everted membrane vesicles. BIBLIOGRAPHIC REFERENCES: Harold, F.M. Membranes and Energy Transduction in Bacteria. Current Topics in Bioenergetics 6:83-149 (1976). Harold, F.M. Vectorial Metabolism. In: The Bacteria (L.N. Ornston and J.R. Sokatch, editors), Vol VI (1977) Academic Press, in press.